Alloy for surgical needles



Patented Jan. 2, 1934 1 1,942.13 ALLOY roa summon. Nsanuis Wilhelm man, Hanau-on-the-Maln, Germany No Drawing. Application July so, 193:, Serial No. 627,117, and in Germany August 8, 1931 1 Claim. (Cl. .75-1) This invention relates to sursical sewing needles, dental instruments and instruments or a like character or which have in use to comply with like requirements. Surgical sewing needles require above all considerable stillness and extremeiy high elasticity in order that the surgeon, particularly when using curved surgical needles, can be completely certain of the path whichthe needle will take in the tissue to be sewn. Further more the elasticity must be so high that the eye when split tor transversely inserting the thread can be opened without breaking, and alter the insertion of the thread is automatically closed tightly and completely.

For these reasons surgical sewing needles have hitherto been successfully manulactured only lrom hardened steel, and all attempts to make such needles from stainless steels or corrosionresistant alloys have so far failed, because no corrosion-resistant metallic material has, up to date, presented sufllcient stillness combined with sufllcient elasticity.

The usual steel needles also have the disadvantage that it: they are bent too much they break.

According to the invention surgical sewing needles are made from heat-treated nickelberyllium alloys which may also include additions or other elements tending to increase the stillness and elasticity. Extensive researches have shown that even binary nickel-beryllium alloys containing from 1 to 3% beryllium are equivalent in the heat-treated condition, as far as stillness is concemed, to hardened and tempered carbon steel,

and they even surpass this to a small extent. The

elasticity also clouly approaches that of hardened and tempered steel, while with proper fabrication nickel-beryllium alloys become substantially tougher than hardened and tempered steel.

In many cases the stiffness and elasticity of binary nickel-beryllium alloys are not good enough, for example for very thin and long needles. In such cases the stillness and elasticity can be further increased by suitable additions or one or more. or the elements chromium in amounts of up to 25%, molybdenum in amounts or up to 12%, tungsten in amounts of up to 18%, and cobalt up to 10%. The beryllium content or such ternary and complex alloys may actually be lower than in binary nickel-beryllium alloys for obtaining the same hardness and the same capacity of being improved by heat treatment; amounts of 0.3 to 2.5% are sufllcient. Furthermore some or the nickel content. that is to say upto25%,canbereplacedbyiron,butinno 0.3xto 3% beryllium,

cient resilience for spring eyes.

caseshould the nickel content mu below 40% or the alloy ii any corrosion attacksare to be 'met with certainty.

The alloys may advantageously contain from 0 to 25% of iron, 0.3 to 3% oi. beryllium, 10 to 20% of chromium, and either 4 to 10% of molybdenum or 2 to 5% of molybdenum and 3 to 8% of tungsten, or 2 to 5% of molybdenum, 3 to 8% of tungsten and 1 to 5% of cobalt, the remainder in each case being nickel except that small additions of such elements as manganese (about 0.5 to 3%), silicon (about 0.05 to 0.2%) and like elements may be included for the purpose ofv facilitatin and improving the steps of fabrication by rolling and drawing. As one particularly suitable alloy for the manufacture of surgical sewing needles there may be'mentioned an alloy containing from 15% chromium, 7% molybdenum, 15% iron and the remainder nickel.

A semi-circular surgical needle curved to a radius of 15 mm. made from the alloy mentioned above and having a stem thickness or from 1 to 1.2 mm. has a chord of 30 mm. measured from the point to the eye; such a needle can be held; until the distance between the point and the eye is 20 mm. and when released will spring back .to the original chord of 30mm. If, however," it is bent until the distance between the point and the eye is less than 15 mm it'takes a small permanent set, whereas a needle of hardened steel subjected to such a treatment would break. Needles with'so-called spring eyes, that is eyes split longitudinally for the purpose of transverse introduction of the thread, behave entirely satisfactorily thanks to the remarkable elasticity and toughness of these alloys, and in fact the spring eyes of such needles break less easily than those of needles made of hardened steel. Surgical sewing needles hitherto made of corrosion-resistant materials have practically without exception ,been' made without spring eyes, since the corrosion-resistant materials hitherto known and suitable for themanuiacture of needles it was not possible to obtain sum In the manufacture of surgical sewing needles from the said alloys it is advantageous to heat and quench for the last time before fabricating the needles to their final dimensions. Thereafter the needles are brought to their flnaldimensions by cold working which brings about a substantial increase in the hardness and elasticity, and only after the needles have been considerably hardened by cold working are they subjected to a tempering heat treatment. Inthis way it is posdental probes and other surgical and dental instruments and appliances. Specially the dental probes, nerve needlesand the like must have great toughness besides extremely high elasticity, because needles broken in the tooth practically always lead to loss of the tooth. Such probes and nerve needles are frequently also used substantially better in this respect than the to introduce acids into the nerve canal of a tooth; the particularly high corrosion-resistance necessary ior'such instruments is present in needles made of nickel-beryllium alloys with addition of chromium and molybdenum which are binary nickel-beryllium alloys.

I clalm:-- f

Surgical sewing needles, dental instruments and the like which require considerable stiflness and elastichardness, made from an alloy containing iron up to 25%, beryllium 0.3 to 3%, chromium 10 to 20%, molybdenum 2 to 5%, tungsten 3 to 8%, and cobalt 1 to 5%, the remainder being nickel. I 

